Fluid entry analyzer



April 30, 1963 K. c. CRUMRXNE FLUID ENTRY ANALYZER Filed Dec. 22, 1958 FIG. I

FIG. 2

Kenneih C. Crumrine inventor By fi Afiorney 3,088,026 FLUID ENTRY ANALYZER Kenneth C. Crumrine, Tulsa, Okla., assignor to Jersey Production Research Company, a corporation of Delaware Filed'Dec. 22, 1958, Ser. No. 782,187 l Claim. (Cl. 250-43.5)

This invention is broadly concerned with a system of logging a completed well so as to determine the points of entry within the well of different fluids such as oil, gas, and water. The invention is more particularly concerned with a method of loggingawell with a gamma-gamma type logging tool while the" well is actually producing so as to determine the transmissibility of the fluidspresent along the well for gamma-type: radiation. In a preferred embodiment of the invention, the fluids flowing within a well are funneled or otherwise directed between a source and a detector of gamma radiation so as to measure their transmissibility forsuch radiation.

In drilling a well such as an oil well, it is known that one may encounter not only formations. producing oil but also other formations producing gas or water. It is further known that, during the production history of an oil well, a formation originally producing only oil may tend to produce progressively more-and more gas or'water along with oil. Thus, most producing oil reservoirs have a'natural 'gas cap or an underlying aquifer which tends to expel oil from the reservoirs. As oil is produced from such a reservoir, the gas or water enters portions of the reservoir previously occupied by the oil; and-it is produced alongwith the oil. The term oil contrasted to gaseous hydrocarbons.

Since oil is a generally more valuable and desirable product than either 'gas or water, it is usual practice within the oil industry to restrict the production of water and gas from-producing oil wells. Further,'by restricting or limiting the production of such gas or water, the oil-producing eflect of these fluids is prolonged.

In order to selectively prevent the flow of gasor Water from an oil well, it is first necessary to know the .points of entry of the various fluids within the well. Once the points of entry are known, itispossible to take one or more remedial steps of a conventional nature to prevent the flow of gas and water'and'to promote the flow of oil.-

It is, accordingly, anobject-of'this invention to provide an improved method-forlocating the points of entry of oil, gas, and water within-a completed well. It is a :more particular'object to providean improved method of logging which is able to locatesuch pointsofentry with in-- creased accuracy. The invention has as an especial object the location of the points of entry of water and gas within a producing oil well.

These and related objects of the invention will be expressly discussed or readily apparent in the following description. The objects of the invention will also be more readily understood by reference to the attached drawing in which:

FIGURE 1 is a longitudinal cross-section view of a logging tool contemplated to be particularly suitable for the practice of this invention.

FIGURE 2 is a sectional view of a producing oil well showing how the tool of FIGURE 1 may be used in locating the points of entry of water within the well.

Referring first to FIGURE 1, the tool illustrated there includes an elongated rod-like body member 10, a first flange-like end member 11, a second flange-like end member 12, and flexible flow guides 13 and 14 attached to the end member. Members 10, 11, and 12 may be constructed of any suitable material-as, for example, steel.

hydrocarbons as .asused in this description, it should be noted, isintended to mean liquid 2 It is necessary, however, that'rnember 12 be constructed of a material which will pass gamma-type radiation. The flow guides should be constructed such that'the tool may travel freely in either direction within the well. A particularly desirable design is that shown in FIGURE 1, in which each guide comprises a plurality of flexible wirelike members. Constructed in this fashion, the. guides act as centralizers and center the logging tool within av well. They also act to mix or disperse any fluids flowing. within the well as they pass the tool. They also tend to funnel the fluids into the path of gamma radiation.

A source 15 of gamma radiation such as radioactive cobalt, iridium, arsenic, or radium is mounted Within end member 11 so as to be symmetrical with respect to the axis of the tool, and alsotoface toward the opposite end member 12.

Gamma ray detector or counter 16 is mounted within end member 12 and sealed therein so as to beout of direct contact with well fluids. Like source 15, detector 16 is preferably symmetrical with respect to the .axis of the logging tool; and it is arranged so as to be sensitive toradiation emitted from source 15. A bundle of conventional Geiger tubes may be used as the detector.

The output from detector 16 is preferably preamplified directly within end member 12. It is then conveyed to the surface of the earth through a cable or equivalent means 17.

I The spacing of the source 15 from the detector 16 may be varied as desired. The radiation path, however, needs to be long enough to givegood averaging of fluids but short enough to give good resolution in depth. In general, a distance of about 12. to 24'inches will suflice for most well installations. Relatively greater spacings are required in those instances where the well fluids to be differentiated approximate each other in their density char acteristics.

In addition to source-detector spacing, it will be-recognized that other factors such as logging speed, fluid flow rate, etc., may be varied as desired to improve the effectiveness of the method of this invention.

Having described a tool of the invention in FIGURE 1, attention is next directed to FIGURE 2 to explain in greater detail the manner in which the tool of FIGURE 1 may be employed. FIGURE 2 depicts a well 20 which extends from the earths surface down through producing formation 21; The well'is lined with casing 19 which is cemented in position by means of cement '22. The casing is perforated at three separate intervals 23, 2-4, and 25' laterally opposite formation 21.

A string of production tubing 26*extends from the wellhead down the well to the packer 27 which is positioned in this instance slightly above formation 21. The Wellhead 28 includes cross 29 and four valves 30-33, inclusive. For the sake of this description, it will be assumed that valve 32 leads to suitable surface storage equipment; and this valve plus valve 33 will then normally be open when well 20 is producing.

Valve 30 may serve a number of purposes. Among such purposes, for example, it may be used to admit fluid into the well Whenever it is desired to kill the well.

Valve 31 is shown to be connected to a length of tubing .35 which terminates at its upper end in lubricator 36. Lubricator 36 has a drain line 37 through which fluid may pass to release well pressure from tubing when the logging tool is located in the tubing and valve 31 is closed. Further, fluid may be circulated through line into tubing 35 and thence out through line 37. A fluid to be used in calibrating a well-logging tool could thereby be placed to surround the well-logging tool in tubing 35.

As illustrated in FIGURE 2, the logging tool of FIG- Patented Apr. 30, 1963" URE 1 is shown to be suspended within well '20 by means of cable 17. The cable extends up through tubing 26, cross 29, valve 31, and tubing 35. It then passes through lubricator 36 around sheave 40 to suitable surface equipmerit-not shown-for raising and lowering the cable. Signals from the detector portion of the tool are transmitted through the cable to surface amplifier 41 and then to a suitable indicator or recorder 42.

In further describing the operation of well 20, it will be assumed that water is being produced in excessive quantities along with oil from formation 21. It will further be assumed that it is desired to determine which set or sets of perforations are passing the water in order that these perforations may be sealed 011.

With these assumptions in mind, and with the logging tool lowered within the well through the tubing 18, the well is produced at rates sufiicient to flow detectable quantities of both oil and water. Generally speaking, a production period of about one-half to one hour will be sufiicient in most instances for the purposes of this invention.

At this point, the logging tool is lowered to the bottom of the well; and it is then gradually raised within the well. As it is raised, detector 16 emits a signal through cable 17 which is related in magnitude to the transmissibility of gamma rays through the well fluids flowing between source and detector 16 at each point within the well 20. Fluid relatively rich in Wateras compared to oilwill display a lower transmissibility for gamma radiation than will a mixture of the same oil and water which is richer in oil than water. Thus, assuming that water is entering the perforations 25-but not perforations 23 or 24-the signal from detector 16 will increase substantially as the logging tool rises to the level of perforations 24.

In order to increase the sensitivity of the logging tool in the operation just described, the tool may be precalibrated for fluids existing within the well before the tool is actually lowered in the well. For example, separate samples of oil and water produced from formation 21 may be placed in suitable containers at the surface of the earth; and the logging tool may then be submerged within the sample fluids in order to measure the transmissibility of gamma radiation through the fluids. The characteristic signals determined in this manner will normally vary somewhat from the signals actually realized within a well, but the relative magnitudes of the signals will normally remain about the same.

Once it has been determined which perforations within the well are flowing water into the well, conventional techniques such as squeeze cementing may be used to seal these perforations.

If a first pass of the logging tool Within the well 20 does not reveal a sharp break in the output signal from detector 16, the operation may be repeated until such a break becomes evident. Difliculty in recognizing the break is not to be unexpected, since the output signal from the detector will seldom-if ever-be constant in magnitude. The random nature of radiation emission and detectiontogether with the presence of natural radiation from within the surrounding formationsare in the main responsible for this condition.

As will be apparent to persons skilled in the art, the major purpose of tubing 35 is to facilitate the insertion and removal of the logging tool into and out of the well 20. The projections extending laterally from the tubing aid the operator in reaching the lubricator 36.

A number of variations in the methods described above may be practiced without departing from the spirit or scope of the invention. For example, a well to be logged may first be killed with water, Where Water is not harmful to the well. The well in this instance is thus filled with a substantially uniform fluid. The well may then be logged in accordance with the invention, first while the well is killed and then after the well has been on production.

It is also apparent that the method of this invention may be used to detect the points of entry of water within a gas well, gas within an oil well, etc.

The invention claimed is:

An apparatus for logging a well comprises an elongated rod-like body member adaped to be moved within a well, a separate flange-like end member attached to each end of said body member, a plurality of flexible fingerlike members attached to the periphery of each end member and arranged to act as centralizers for said apparatus within a well, a source of gamma radiation mounted on one of said end members and arranged symmetrically relative to the axis of said body member in a manner to irradiate the cross section of a well around said body member, and a gamma radiation detector mounted in the other of said end members and arranged symmetrically relative to said body member in a manner to detect gamma radiation emanating from the cross section of a well around said body member.

References Cited in the file of this patent UNITED STATES PATENTS 2,725,486 Walstrom Nov. 29, 1955 2,761,977 McKay Sept. 4, 1956 2,833,929 Barieau May 6, 1958 2,873,377 McKay Feb. 10, 1959 2,882,417 Johnson Apr. 14, 1959 2,926,259 Dewan Feb. 23, 1960 2,932,740 Widmyer Apr. 12, 1960 2,961,539 Egan ct al. Nov. 22, 1960 2,963,583 Lebourg Dec. 6, 1960 2,965,753 Reynolds et al. Dec. 20, 1960 

